The Marangoni convection on the silicon melt surface in Czochralski method was investigated. The results showed that Marangoni convection is related strongly to oxygen in silicon. Introducing a magnetic field by NdFeB permanent magnet into the melt, when (B) over right arrow --> (B) over right arrow (0) ((B) over right arrow (0) is the critical value), all the macro-convections were restrained in the melt and the Marangoni convection on the free surface emerges and becomes dominant. The oxygen concentration in silicon can be controlled freely by the Marangoni convection. (C) 2003 Elsevier Science B.V. All rights reserved.